| Year | Value | | 2022 | 43.485830124257 | | 2021 | 42.693459220204 | | 2020 | 41.2424529392 | | 2019 | 41.518581820096 | | 2018 | 42.242804435892 | | 2017 | 42.609768455152 | | 2016 | 42.007214417255 | | 2015 | 42.837254157452 | | 2014 | 44.837382813784 | | 2013 | 44.652757904885 | | 2012 | 45.877885334946 | | 2011 | 46.67350031622 | | 2010 | 48.331801265348 | | 2009 | 47.145880045093 | | 2008 | 48.433846090316 | | 2007 | 47.06715167496 | | 2006 | 45.403212203414 | | 2005 | 43.247820563174 | | 2004 | 42.650705091086 | | 2003 | 39.879395924351 | | 2002 | 37.043420286907 | | 2001 | 35.929864074694 | | 2000 | 34.744197140388 | | 1999 | 34.611626947425 | | 1998 | 36.577581563983 | | 1997 | 37.958107700455 | | 1996 | 37.090012033781 | | 1995 | 37.953116424015 | | 1994 | 39.975581432217 | | 1993 | 39.796238263475 | | 1992 | 38.369321065967 | | 1991 | 36.474186996212 | | 1990 | 34.985298387977 | | 1989 | 34.552561816891 | | 1988 | 36.071879512187 | | 1987 | 35.334830410693 | | 1986 | 33.150402636833 | | 1985 | 33.287697457432 | | 1984 | 33.127193191203 | | 1983 | 31.825074661524 | | 1982 | 31.676435995985 |
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